This invention relates generally to catheters adapted to be inserted into the cardiovascular system of a living body and, more particularly, to an improved catheter having an improved distal end portion for more precise location in the particular artery of the cardiovascular system.
Catheters are often used in the performance of medical procedures such as coronary angiography for injecting dye, or the like, into the cardiovascular system for diagnosis; and angioplasty to widen the lumen of a coronary artery which has become at least partially blocked by a stenotic lesion causing an abnormal narrowing of the artery due to injury or disease. In these techniques the distal end of the catheter is introduced into the aorta by way of the femoral artery. The proximal end of the catheter is then manipulated so its distal end is inserted into the lumen of a selected coronary artery branching off from the aorta. A typical angioplasty procedure would involve initially inserting a guiding catheter into the cardiovascular system in the above manner, followed by a dilating catheter, a laser catheter, an atherectomy catheter, or the like, which is guided through the guiding catheter until its distal end portion is positioned within the stenotic lesion in the coronary artery to reduce the blockage in the artery. A diagnostic catheter would be used in the same manner.
The most common catheter used in treatment of the left coronary artery is what is often referred to as a "Judkins" catheter which has a specially shaped distal end portion for facilitating insertion into the artery. However, as will be specifically discussed, there are some disadvantages to the "Judkins" catheter, including its inability to align perfectly coaxially with selected artery and thus permit optimum treatment, and its inability to adequately support other devices such as balloon catheters. Also, the Judkins catheter forms relatively large angles when inserted into the cardiovascular system thus dissipating some of the axial forces transmitted through the catheter during use.
The Judkins-type catheter originally was designed and used for diagnostic angiography. However, with the advent of angioplasty, the Judkins-type catheter has been used routinely for about the last fourteen years to guide balloon catheters and other intravascular devices through the vasculature to the left main coronary artery. The overall shape/configuration of the Judkins-type catheter has remained basically the same throughout this period. Although some variations in its shape/configuration were made, the basic overall shape of the Judkins-type catheter has not been specifically adapted for the unique needs dictated by angioplasty procedures. Instead, the Judkins-type catheter (as commonly used in a left femoral approach technique for intubating the left main coronary artery) has been adapted only slightly from its original configuration that was designed for diagnostic angiographic procedures.
Accordingly, the Judkins-type catheter presents several difficulties when used for angioplasty procedures. Significantly, the principle problem associated with the use of a Judkins-type catheter as a guiding catheter is the lack of backup support which results in several undesirable consequences. When a Judkins-type guide catheter is disposed in the cardiovascular system and one attempts to push the balloon catheter distally across a tight stenosis, a resultant (opposite proximal) force is generated by the balloon catheter against the guide catheter. This problem is described in depth in Danforth U.S. Pat. No. 4,909,787. The result is that the tip of the Judkins-type catheter may become dislodged from the ostium of the left main coronary artery, i.e., the distal portion of the catheter "prolapses" and loses its preferred orientation within the ascending aorta and left main coronary artery. After this occurs, further advancement of the balloon (or other) working catheter becomes nearly impossible because the Judkins guiding catheter no longer provides adequate support to the highly flexible shaft of the balloon catheter as one attempts to push the balloon catheter across the tight stenosis.
Various attempts to solve this problem are described in the prior art. One of these attempted solutions is set forth in Danforth U.S. Pat. No. 4,909,787 which describes a modified Judkins-type guiding catheter in which the "secondary curve" of the catheter includes a controllable stiffening means. This stiffening means is activated when the Danforth catheter is disposed within the cardiovascular system so that when one attempts to push a balloon catheter across a tight stenosis, the stiffening means on the outer curvature of the secondary curve counters the force exerted against the guide catheter because of the resistance of the stenosis. This stiffening means is said to maintain enough rigidity in the guiding catheter to maintain the tip portion of the guiding catheter within the ostium of the left main coronary artery thereby preventing prolapse of the guiding catheter. Similarly, Danforth U.S. Pat. No. 4,822,345 provides an inflatable/deflatable balloon 50 which works in a manner similar to the catheter in the Danforth U.S. Pat. No. 4,909,787 to increase the rigidity of the distal end of the guiding catheter. Both of these references describe modified Judkins-type guide catheters in which it was attempted to increase balloon catheter backup support by increasing the stiffness of the outer curvature of the distal end portion of the guide catheter and thus prevent the guide catheter from prolapsing during balloon catheter advancement distally across a stenosis. Neither of the Danforth patents attempted to make a fundamental change in the overall shape/configuration of the Judkins-type guide catheter to solve the problem of inferior backup support.
Shiu U.S. Pat. No. 5,098,412 describes a Judkins-type guide catheter having a secondary lumen in addition to a main lumen through which a balloon catheter passes. The secondary lumen structure is separable from the main lumen at the distal portion so that when a distal end of the main lumen of the guide catheter is intubated in the ostium (LMCA), the secondary lumen is moved away from the main lumen (at the distal portion) and may be braced against the opposed walls of a vessel to retain the position of the guide catheter. As in the other attempted solutions to the problem of balloon catheter back up support, the Shiu approach adds bulky complex structure to a Judkins guide catheter instead of fundamentally altering the basic configuration of the Judkins guide catheter to solve the problem. Despite the modification of the Judkins guide catheter, the Shiu guide catheter retains the overall configuration of the Judkins catheter that results in the apex of the secondary curve portion of the Judkins-style guide catheter "banking" of the wall of the ascending aorta at a location substantially above the ostium.
Other solutions include trying to "lock" the tip portion of the Judkins-type guiding catheter within the ostium of the left main coronary artery. For example, Patel U.S. Pat. No. 5,000,743 discloses an inflatable balloon on the distal end of the guide catheter for securing the distal end within the lumen of a coronary artery. Alternatively, Patel U.S. Pat. No. 4,781,682 discloses another type of Judkins-type guide catheter with a "locking" device consisting of support flaps, which expand from the outer surface of the guide catheter, to anchor the distal end portion of the guide catheter adjacent the left main coronary artery. However, these attempted solutions have their own undesirable results. The former solution impedes blood flow through the left main coronary artery and the latter solution introduces additional bulky structure into the cardiovascular system which may hamper the blood flow and interfere with the functioning of the aortic valve. Similarly, Duess U.S. Pat. No. 5,122,125 describes a Judkins-type guide catheter having a "centering" or "locking" top portion in which ridges on the outer surface of the distal tip portion effectively wedge against the inner walls of an ostium to center the tip portion within the ostium. This feature is said to allow proper blood flow around the distal tip portion as well as effectively "anchor" the distal tip portion within the ostium thereby insuring stable and precise positioning of the guide catheter.
These previous modifications of the Judkins catheter for angioplasty have not addressed the primary reason for frequent prolapse of the Judkins-type guide catheter when advancing a balloon catheter across a stenosis: the overall shape of the Judkins guide catheter (prior to insertion in the cardiovascular system) is poorly designed for angioplasty purposes. There are several features of the basic shape of the Judkins guide catheter (for left main coronary arteries or "LMCA") that cause poor performance in using Judkins or slightly modified Judkins guide catheters in angioplasty procedures.
The main deficiency in the previous attempted modifications of the Judkins catheter (as used for guide catheter purposes in the LMCA) has been a lack of appreciation for the extent to which the shape of the Judkins guide catheter prior to insertion in the cardiovascular system affects its performance (i.e., coaxial positioning, backup support) when the Judkins guide catheter is disposed within the cardiovascular system.
The first deficiency in the shape of the Judkins catheter is that the primary curve of the Judkins guiding catheter forms a 90.degree. right angle prior to insertion in the cardiovascular system and is relatively inflexible (the primary curve corresponds to the first curve in the catheter proximal of its utmost distal end). This causes the distal tip portion of the Judkins-type catheter to be incapable of aligning coaxially within the ostium of the left main coronary artery. The 90.degree. angle of the primary curve hampers the ability of the balloon catheter to exit the tip portion of the guiding catheter because this frequently causes the balloon catheter to exit the tip portion into the wall of the left main coronary artery. Accordingly, deep intubation of the distal tip portion within the ostium, which is desirable to increase support for advancing a balloon catheter across a stenosis, is extremely difficult and not practical with the Judkins guide catheter. Moreover, this 90.degree. primary curve also generally limits the distance which the distal tip portion may be intubated into the left main coronary artery.
Similarly, this misalignment of the tip portion prevents the full transfer of pushing force from the proximal end of the balloon catheter to the distal end of the balloon catheter because the balloon catheter must bend around the steeply angled primary curve tip portion of the Judkins-type catheter before aligning properly within the ostium and lumen of the left main coronary artery. This problem with the Judkins guide catheter when used for angioplasty is directly attributable to the belief that one must prevent intubation of the Judkins guide catheter within the ostium and the LMCA. This belief was based on the strong reluctance to put such a catheter into the left main coronary artery because of the relatively large size of diagnostic catheters at time of development of the Judkins catheter.
Moreover, the 90.degree. angle primary curve causes particular problems when attempting to maneuver a balloon catheter into the circumflex branch of the left main coronary artery. The circumflex branch extends from the ostium in the left main coronary artery in a direction almost directly opposite the exit of the balloon catheter from the distal tip portion of the 90.degree. primary curve of the Judkins guide catheter. Accordingly, when attempting to maneuver a balloon catheter into the circumflex branch, the balloon catheter must first negotiate the 90.degree. primary curve of the Judkins catheter and then completely reverse direction (about 180.degree.) to enter the circumflex branch of the left main coronary artery. This significantly attenuates pushing forces transmitted from the proximal end of the balloon catheter to the balloon portion thereby making the crossing of a lesion or stenosis much more difficult.
However, the sharp 90.degree. angle of the primary curve is not the only feature of the shape of the Judkins guide catheter that hampers coaxial placement and stable positioning of the distal tip portion within the ostium of the left main coronary artery. The other main feature of the Judkins guide catheter (for LMCA) is a long straight segment extending distally of the secondary curve (and proximal of the primary curve) and the absence of any other significant curves formed along the length of the catheter (other than the conventional 180.degree. secondary and conventional primary curve). This creates several consequences which combine to cause noncoaxial ostial positioning and poor backup support of the Judkins guide catheter for LMCA.
The first consequence of having the long straight segment extending distally of 180.degree. secondary curve is that when the distal tip and primary curve portion of the Judkins guide catheter are positioned within the ostium of the LMCA, the long straight segment of the Judkins guide catheter distal of the secondary curve (and proximal to the primary curve) extends upwardly from the ostium and across the ascending aorta at a substantial (i.e., sharp) angle so that the Judkins guide catheter contacts the wall of the ascending aorta substantially above the ostium of the LMCA. After contacting the wall of the ascending aorta, the Judkins guide catheter extends proximally away from the aortic wall at a substantial angle (relative the aortic wall) toward the arch of the aorta before again contacting a wall of the descending aorta adjacent the arch of the aorta. Thus, the Judkins guide catheter effectively banks off the wall of the ascending aorta.
The long straight segment extending distally of the 180.degree. secondary curve portion is significant because it is that segment which allows the distal end portion of the Judkins catheter to become anchored within the aortic root complex. This long straight segment (distal of the secondary curve portion) is noticeably longer than the diameter of the ascending aorta and has the following effect: when the utmost distal tip and primary curve portion of the Judkins catheter are intubated within the ostium of the left main coronary, the long straight segment (distal of the secondary curve portion) becomes "wedged", i.e., anchored between the ostium (of LMCA) and the wall of the ascending aorta (where the apex of the secondary curve portion contacts the wall). Without this long straight segment distal of the secondary curve portion, the Judkins guide catheter would slip against the wall of the ascending aorta as one attempted to further advance the guide catheter into the ostium, thereby causing unstable positioning of the Judkins guide catheter.
Accordingly, the long straight segment distal of the secondary curve portion of the Judkins guide catheter is made appreciably longer than the diameter of the ascending aorta so that this "wedging" phenomena occurs. It is because this long distal straight segment is appreciably longer than the diameter of the ascending aorta that the apex of the secondary curve portion contacts the ascending aortic wall substantially above the ostium of the left main coronary artery.
The portion of the Judkins guide catheter that contacts or "banks off" the ascending aortic wall (the contact portion) corresponds roughly to the apex of the curvature of the 180.degree. bend secondary curve. This contact portion is relatively small and approximates a single point on a line such that the contact portion will act as a localized pressure point on the wall of the ascending aorta. It is generally desirable to spread out any pressure exerted on a wall of a blood vessel such as the ascending aorta.
More importantly, the small size of the contact portion in its location substantially above (not directly across from) the ostium of the LMCA directly cause the poor backup support of the Judkins guide catheter when advancing a balloon catheter across a stenosis. First, because the surface area of contact between the contact portion and the aortic wall is so small, the Judkins guide catheter is much easier to dislodge from its position against the wall when resistive "pushback" forces are encountered during advancement of a balloon catheter across a stenosis. Moreover, the straight portion of the Judkins guide catheter (distal of the secondary bend) extends downward through the ascending aorta substantially lateral relative to the contact portion. This allows the stenotic "pushback" forces to more easily overcome the friction of the small contact area between the Judkins guide catheter and the aortic wall and dislodge the Judkins guide catheter from the desired orientation in the aortic complex. However, the potential for dislodging the Judkins catheter from its desired position is not the most disadvantageous aspect resulting from the overall configuration of the 180.degree. secondary curve, 90.degree. primary curve and absence of other curved portions in the Judkins guide catheter.
As explained earlier, the most significant problem associated with the basic shape of the Judkins guide catheter is prolapse (i.e., retracting or "backing out" of the distal tip) of the Judkins catheter from the ostium when advancing the balloon catheter. Prolapse of the Judkins guide catheter occurs because the "pushback forces" are directed along an axis generally parallel to the ostium of the left main coronary artery through the ascending aorta whereas the Judkins guide catheter point of support is a small contact point substantially above the ostium. The stenotic "pushback" forces tend to push the distal tip portion of the Judkins catheter out of the ostium and toward the opposite wall of the ascending aorta. During this prolapse of the distal tip portion, the apex of the secondary curve of the Judkins catheter rests against the aortic wall and acts as a hinge allowing the straight portion (distal of the secondary curve) to bend backwards toward the opposite wall.
The prolapse of the Judkins guide catheter when advancing a balloon catheter is a direct consequence of having a small point of contact against the aortic wall substantially above the ostium. The Judkins guide catheter lacks support to counter pushback forces where it needs it most; directly across from the ostium. The basic positioning of the Judkins guide catheter within the cardiovascular system and ascending aorta is dictated by the basic shape of the catheter when in a relaxed state prior to insertion. In particular, the long straight segment extending distally from the 180.degree. secondary curve (and lack of other curves throughout the length of the catheter other than the primary curve) result in this positioning within the ascending aorta substantially above the ostium of the left main coronary artery. Moreover, recall that attempted solutions (in the Danforth patents) to rectify the prolapse problem of the Judkins guide catheter did not recognize that the basic shape of the Judkins guide catheter was the cause of the prolapse but rather merely added structure to the same basic shape in an attempt to prevent prolapse. Likewise, the Patel patents did not recognize that the problem of prolapse is caused by the basic shape of the Judkins catheter but rather tried to anchor the distal tip portion of the catheter near the aortic root to "lock" the guide catheter within the aortic complex near the ostium. None of the attempted solutions recognize, must less solve, the problem with the Judkins guide catheter--its basic shape prior to insertion in the cardiovascular system--a combination of a primary curve with a 90.degree. angle, a 180.degree. secondary curve with a long straight segment extending distally therefrom, and no other curves throughout the length of the catheter. This configuration results in the absence of a point or axis of support directly across from or opposite the ostium of the left main coronary artery.
Another problem with the Judkins guide catheter is that each bend in the Judkins guide catheter (when disposed fully in the aorta complex) forms at least a 90.degree. angle and or an acute angle (less than 90.degree.). Acute (or 90.degree.) angles in the Judkins catheter cause great resistance to pushing the balloon catheter through the Judkins guide catheter. This happens because the Judkins catheter prior to insertion has only two large curves including the 180.degree. (or 150.degree.) secondary curve and the 90.degree. primary curve, and has no other curved portions throughout its length.
This is significant because the catheter must trace a 180.degree. path around the arch of the aorta and then another 90.degree. turn into the ostium of the left main coronary artery creating an overall path from the descending aorta to the ostium of the LMCA of about 270.degree.. Having fewer curves in the catheter prior to insertion in the cardiovascular system means that as the guide catheter traces this 270.degree. path each curve will form a greater (i.e., sharper) angle and thus, each acute angle will proportionately reduce the transmission of pushing forces when distally advancing a balloon catheter. Conversely, having more curves throughout the length of the catheter in a relaxed state prior to insertion in the cardiovascular system will mean that each curve can form a more moderate (obtuse) angle when the guide catheter is disposed in the cardiovascular system and in particular, the aortic arch and ascending aorta. This allows for an overall better transmission of pushing forces because no single curve will form less than a 90.degree. angle.
The problem of 90.degree. or acute angled (90.degree. or less) bends in the Judkins catheter when fully disposed in the aortic complex illustrates the poor design of the Judkins guide catheter for supporting distal advancement of a balloon catheter through the Judkins guide catheter. Had the Judkins catheter been designed for angioplasty, the configuration of the Judkins guide catheter would incorporate a combination of curved portions so that when disposed in the aorta, the angles of the bends would be milder, i.e., obtuse, to facilitate a fuller transmission of distal pushing forces in the balloon catheter.
Thus, several main problems are attributable to the basic shape of the Judkins guide catheter. First, coaxial intubation is difficult with a 90.degree. primary curve. Second, the point of support of the Judkins guide catheter against the aortic wall acts as a hinge to allow prolapse of the distal tip out of the ostium because the point of support is substantially above the ostium. Moreover, the small surface area of contact between the contact portion and the aortic wall makes it easy to displace the catheter when stenotic pushback forces are encountered. Third, acute angles of the Judkins catheter (when disposed within the aortic complex) reduce the transmission of pushing forces from the proximal end of the balloon catheter to its distal end when attempting to advance the balloon catheter across the tight stenosis.